Forecast models from sources including the Met Office and European ensembles show a consensus maximum of 17–18°C for Warsaw on September 26, driven by persistent overcast skies, light southwesterly flow, and building high pressure that suppresses daytime heating. Recent observations confirm a cooling trend from mid-September peaks near 20°C, with dew points near 10–11°C and minimal solar insolation under 90–100% cloud cover limiting the diurnal range. This alignment explains the market’s heavy weighting toward 18°C (56%) and 17°C (37%), while slim odds on 19°C or higher reflect residual model spread in boundary-layer mixing. Resolution will hinge on official Polish meteorological station readings, with final data releases expected shortly after sunset on the 26th.